Common to most operating BWR's, the core spray cooling water is delivered to the reactor core region by a core spray line 10 internal to the reactor vessel. A portion of this internal piping is a horizontal segment 12, which is formed to follow the radius of curvature of the reactor vessel wall. The proximal end 14 of this horizontal core spray line 10 is connected to a T-Box 16 at the core spray nozzle penetration. The distal end 13 of this horizontal core spray line is welded to a short radius elbow 17. The weld joining the distal end 13 of the core spray line 10 to the short radius elbow 17 is designated as the P4a weld. A vertical downcomer pipe 18 is welded to the opposing end of the short radius elbow 17. The weld joining the downcomer pipe 18 to the short radius elbow 17 is designated as the P4b weld. This piping configuration and associated connecting welds are shown in FIGS. 1 and 2.
The core spray piping systems in operating BWR's are of welded construction. The welds in the original core spray line 10 are susceptible to Intergranular Stress Corrosion Cracking (IGSCC). In the event that cracking should occur in the P4a weld or the P4b weld, the structural integrity of the core spray line 10, which delivers cooling water to the reactor core would be lost. A preemptive repair would be to design, fabricate, and install a clamping device, which would prevent separation of one or both of the P4a and P4b welds in the event that circumferential through-wall cracking should occur at these weld locations in the core spray line 10.